Along the Chain of Craters Road, Big Island, Hawaii: Part 4

Print Friendly, PDF & Email

Dr Trevor and Chris Watts (UK)

This is the fourth of five articles on the ‘Chain of Craters Road’ on Hawaii’ Big Island. The articles are in the form of a road trip that you can follow if you are lucky enough to go to this wonderful part of the world to see its volcanic scenery. Being a road trip in the USA, distances along the road and by foot are given in yards and miles, while measurements are provided in more European and scientific metric units.

Hawaiian pronunciation
A word about Hawaiian pronunciation – Hawaiians do not say ‘Morna Ulu’ for the Mauna Ulu volcano. They split most vowels up separately: thus, ‘Mah ooner Oo loo’. Similarly, ‘Kill ow eh uh’, for Kilauea; and, ‘Halley mah oomer oo’, not ‘Halley mow mow’, for Halema‘uma‘u; and, ‘Poo ooh Poo ah I’, for Pu’u Pua’i.

3.7 miles: Mauna Ulu

A short road to the east finishes in a large car park. The trail continues eastwards through the woodland (Fig. 1) for a few hundred yards until it opens out to a view of the twin peaks of nearby Pu’u Huluhulu and the more distant, and much higher, Mauna Ulu (Fig. 2).

Fig. 1. A side trail into the forest close to Mauna Ulu car park.
Fig. 2. Where the trail divides left and right. The dark a’a lava spreads across the lighter ash and lapilli flow. The twin peaks form Mount Pu’u Huluhulu; the more distant low rise is the shield volcano, Mauna Ulu.

A’a lava flow: Just ahead, there is the leading edge of an a’a flow, a rough, jumbled wall of rock up to about 6m high (Fig. 3). It was formed during the 1969 to 1974 eruption of Mauna Ulu – its first major eruption. The trail directions are clearly marked here, to the right or the left – both ways are well worth exploring and this area deserves a full article on its own.

Fig. 3. Close to the steep face of the a’a flow.

Lava tree forest: To the left, walking around the a’a flow, the first major feature is a forest of lava tree moulds. Easily accessible, some of these are very large and several have excellent impressions of the trees’ bark on the inside of the central holes (Figs. 4 and 5).

Fig. 4. Two particularly impressive lava tree moulds.
Fig. 5. Fine bark impression on the inner surface of a tree mould.

Spatter ramparts: The second major feature is the site of another fissure eruption. It is linked to the other fissures at Pauahi, close to the north – they are all part of the Eastern Rift Zone complex. This is a particularly fine example of a fissure eruption, with a long and complex spatter-ridge and features you could spend all day photographing (as we have done several times). The lava tubes, long and high mounds of ‘dribble’, blow holes and sink holes are unique in their variety and beauty of form (Figs. 6 to 9).

Fig. 6. First a tree; then a lava mould; then the outlet for a lava vent that spattered and dribbled to form this gorgeous ‘dribble pile’.
Fig. 7. An open fissure that ended its active days as a drain for the surrounding surface lava.
Fig. 8. The rounded surface of this lava tube is swiftly shattering and collapsing.
Fig. 9. The draining-away lava came from the surrounding tree-mould forest and swirled around one last stump before vanishing into the depths.

The range of colours of the lava, especially the pluck lava, is breath-taking (Fig. 10).

Fig. 10. Beautifully-tinted plucks of lava in the roof of a low tube.

Mauna Ulu: Following the leading edge of the a’a flow for around a mile, the heavily-forested slopes of Pu’u Huluhulu come into close view. The trail continues onwards to Napau Campground, but, as it rises around the edge of the woodland, there is a rest point and the start of the climb up to the peak crater of Mauna Ulu. This is the volcano that began its first eruption with huge amounts of lava on 24 May 1969. Over the next four years, it created itself – a whole shield volcano, filling in the pre-existing craters of ‘Ālo’i and Alae. It is still steaming today, both from numerous vents in the slopes and from within the crater.

The climb is not especially difficult, but it can take an hour or more, with frequent pauses to take photographs, to work around obstacles or divert to one side to look at particularly fine lobate flows, small lava lakes with collapse windows into the drained spaces beneath (Fig. 11), miniature lava tubes, and lava tree moulds.

Fig. 11. The lava below simply drained away. The crust is progressively collapsing.

There are also newly colonising plants (Figs. 12 and 13), and pieces of lava that are very varied in colours and formation.

Fig. 12.  Some very hardy succulents are among the first to repopulate the cracks in the bare lava.
Fig. 13. Beautiful ferns also struggle for a tenuous living.

In several places, the crust has fractured where the underlying lava pushed the surface upwards in a mound but didn’t quite break through (Fig. 14) – all this in addition to watching great clouds of steam issuing from above and being very careful on gravelly or wet and slippery slopes (Fig. 15).

Fig. 14. Viscous, rising lava didn’t quite break through at this point.
Fig. 15. The approach to Mauna Ulu’s crater is easy, but ominous.

The peak itself is virtually flat. A stroll of a hundred yards brings you to the sharp drop into the vertically-sided crater (Fig. 16).

Fig. 16. The rim of Mauna Ulu is precipitous and crumbling.

Some parts of the edge are breaking away, so it’s best to be very careful when approaching the rim, especially in high wind and rain conditions such as the last time we visited. The crater measures 135m by 100m and is 100m deep. Although some talus is beginning to accumulate at the bottom, this is still an active crater, with several intermittent steam vents in the inner faces, including a large, cavernous one at the base (Fig. 17). It is highly likely that there will be renewed major activity from this crater.

Fig. 17. The cavernous opening at the bottom of Maun Ulu Crater is one of the origins of the frequent steam clouds.

Walking round the rim is easy and rewarding for the varying views inside, the wider vistas in all directions, and the overflow lava tunnels and channels just below the rim around the other side, on the northeast slope. These outflows have partly overflowed the rim but have also exited through tubes in the side walls, with a convoluted series of channels and spatter ridges (Figs. 18 and 19).

Fig. 18. There are many channels leading away from the rim. In places, they are joined by lava that leaked, tributary-like, through holes in the side of the mountain.
Fig. 19. An outflow channel that collected lava from the surrounding flow, as well as directly from its own source near the rim.

To return to the trailhead near the car park, the easiest way is straight down the slope, as long as the visibility is good. You can see the point where the trail splits close by the a’a flow, and simply head downslope towards it, skirting round the most jagged parts of the flow just before the bottom of the slope. On the way down, there are some excellent areas of gleaming lobate lava (that is, lava that runs in long smooth lobes across the surface, without wrinkling, rumpling or coiling up), pahoehoe lava (Fig. 20), cracked and broken lava tube roofs, vents into lava tunnels, and sparse vegetation beginning to re-populate the land.

Fig. 20. Silvery lobate lava, with coils of pahoehoe.

The varieties and colours of lava to be found within a few paces of each other is extraordinary (Fig. 21).

Fig. 21. (a) A tinted inclusion in vesicular lava; (b) lapilli ejecta; and (c) spatter folded across itself.

Spatter fissures and ramparts: Returning to the trailhead at the a’a lava flow, taking the right turn leads immediately to the highest examples of spatter ramparts (Fig. 22), and also spatter cones that developed during the various eruptions of Mauna Ulu (in 1969, 1973 and 1974).

Fig. 22. The high point of a line of spatter-fissure ramparts, reaching more than 10m.

There are also many drainage holes and long fissures into which the lava escaped (Figs. 23 and 24), often leaving long slurping dribbles down the sides as the last drops solidified.

Fig. 23. Two pits along a massive fissure that gradually closed itself up as the lava began to recede back into the earth.
Fig. 24. Two fissures opened in parallel here. One formed the ramparts that issued the lava; the other took it back.

The views, especially from the tops of the ramparts and cones, are beautiful (Figs. 25 and 26) – near-level, orange and grey ash fields punctuated by elongated ramparts, isolated hornitos/spatter cones… pinnacles… the distant forest… The range of form and colour in the lavas is again remarkable.

Fig. 25. Fractured crust sections and isolated spatter mounds punctuate the undulating ash and lapilli field.

As we say above, the features accessible from the Mauna Ulu parking lot are manifold and deserve much closer coverage than this. However, moving on, it is easy to stay on this trail and circle back to the main road, and walk back to the parking lot – it saves re-tracing your steps and also saves a separate stop, if you cross the road for a quick exploration of the pahoehoe lava flow there.

Fig. 26. Across the ash and fine cinder fields.

In the last of this series of articles, we will look at some more volcanic highlights of the region, including the intriguingly named ‘Pele’s hair’ and her tears and foam…

Almost all the photographs were taken by one of us – Trevor or Chris – except the few that are credited separately. These are available as Public Domain Images from the United States Geological Service (USGS), particularly the Hawaiian Volcanoes Observatory. Innumerable Internet sites provided background information, such as dimensions of craters. The USGS is invariably helpful in answering specific queries and providing access to wider sources. Their weekly publication, ‘Volcano Watch’, is invaluable for general information as well as updates on theories, eruption activity, and trail and road closures and re-openings.

About the authors

Trevor and Chris are keen amateur geologists living near Nottingham, England. They have climbed many volcanoes throughout the world. Sharing the exploration, photography and writing, they have had numerous articles published on the subjects of volcanoes and their other geological interest – dinosaur footprints (including in this magazine). Now retired from her work as a teacher and head teacher, Chris paints in watercolours, silks and pastels, mostly animal portraits and flowers. Trevor, formerly a teacher, headteacher and school inspector, now writes short stories and poetry for competitions, publication and the mental challenge.

The other parts of this series comprise:
Along the Chain of Craters Road: Big Island, Hawaii (Part 1)
Along the Chain of Craters Road: Big Island, Hawaii (Part 2).
Along the Chain of Craters Road: Big Island, Hawaii (Part 3).
Along the Chain of Craters Road: Big Island, Hawaii (Part 4).
Along the Chain of Craters Road: Big Island, Hawaii (Part 5).

Leave a Reply

%d bloggers like this: